A typical communication system consists of an Application Server (AS) that serves a network containing communication links, users, and their end devices. Two or more users on a network, using the same application, begin a session. An AS keeps track of each ongoing session on its network and also maintains information about the users involved. The termination of a user's session due to poor signal quality or excessive network traffic is annoying at best and may well result in undesired application behavior, especially if the user is making an emergency call.
Public safety agencies typically employ Land Mobile Radio (LMR) systems with diverse access technologies and equipment. Public safety users of such agencies often carry more than one end device in order to communicate over different networks. The end devices may employ either analog or digital technology. The end devices may operate on different bandwidths or support disparate networks, with varying standards and protocols and so on. These differences rule out the possibility of communication between different networks, in spite of the end devices providing essentially the same service.
Commercial users and public safety users are allocated different portions of the spectrum. Public safety users get the highest priority for communication between the two types of users and, under certain emergency conditions, may preempt commercial users from their allocated spectrum. As a result of these priority protocols as well as signal strength metrics, public safety users' sessions are sometimes terminated. After termination, the only option the public safety user has is to attempt to start another session on the same network and AS. This may not always be possible if, for example, the network has exceeded its capacity or if a failure has occurred at the AS. Therefore, it is desirable to enable the transfer of a session between different networks that provide similar application capabilities. During emergencies, such as natural disasters like earthquakes and hurricanes, the ability to provide session transfer between networks becomes increasingly desirable as it is likely that a high priority user will encounter poor connectivity and increased network traffic. Session transfer may involve a change of the operating end device, network, and frequency of communication or access technology. Thus, if a user or a group of users experience poor connectivity on a network while using a certain application, it is desirable to transfer the session to another network that will provide them a substantially similar application along with a similar or better Quality of Service (QoS) and priority.
Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help improve understanding of various embodiments. In addition, the description and drawings do not necessarily require the order illustrated. Apparatus and method components have been represented where appropriate by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the various embodiments so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein. Thus, it will be appreciated that for simplicity and clarity of illustration, common and well-understood elements that are useful or necessary in a commercially feasible embodiment may not be depicted in order to facilitate a less obstructed view of these various embodiments.